For thermal printers which perform printing using a print target medium and an ink ribbon stacked on one another, by holding and conveying the ink ribbon and the print target medium between a platen roller and a thermal head, a known arrangement allows the thermal head to be attached to and detached from the platen roller (which allows the thermal head to be switched between an opened state and a closed state) by operating a head lock lever. (See Japanese Patent Application Laid Open No. H10 100493, for example).
Such a thermal printer has a configuration in which the thermal head is supported by a head supporting means swingably mounted to a support shaft. The head supporting means can be swung by turning a turn shaft mounting a contact member which is in contact with the head supporting means. The turn shaft can be turned by operating the head lock lever which includes a hook at its tip. In the pressed state in which the thermal head is pressed into contact with the platen roller, the hook is engaged with an engagement reception shaft provided on the platen roller side.
However, if a configuration is employed which allows the thermal head to be a significant distance from the platen roller with conventional techniques to facilitate maintenance, there is a need to move the turn shaft upward in order to ensure the swinging angle for the head supporting means. This leads to a need to set the distance between the turn shaft and the hook to a great distance. In some cases, this leads to a problem in that the ink ribbon replacement operation is inhibited by the hook located at a position in the opened state in which the thermal head is at a significant distance from the platen roller. If a ribbon supply shaft and a ribbon winding shaft are supported in a cantilever manner, the ink ribbon replacement operation is performed from the open end side of the ribbon supply shaft and the ribbon winding shaft. If the hook is located at a position which crosses the ink ribbon travel route, as viewed from the open end side in the opened state in which the ink ribbon can be replaced, the ink ribbon comes in contact with the hook in the ink ribbon replacement operation. This leads to a difficulty in the ink ribbon replacement operation. Furthermore, if the travel route for the ink ribbon is set to bypass the hook, there is a need to prepare a space for the ink ribbon travel route, leading to a larger scale of the apparatus.